Mesa (vulkan): util: Fix race condition on libgcrypt initialization

[Jason Ekstrand]

Module: Mesa
Branch: vulkan
Commit: ade3108bb5b074013417b31e61b8077ccefb7484
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ade3108bb5b074013417b31e61b8077ccefb7484

Author: Mark Janes <mark.a.janes at intel.com>
Date:   Tue Apr 12 11:52:53 2016 -0700

util: Fix race condition on libgcrypt initialization

Fixes intermittent Vulkan CTS failures within the test groups:
dEQP-VK.api.object_management.multithreaded_per_thread_device
dEQP-VK.api.object_management.multithreaded_per_thread_resources
dEQP-VK.api.object_management.multithreaded_shared_resources

Signed-off-by: Mark Janes <mark.a.janes at intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94904

Reviewed-by: Edward O'Callaghan <eocallaghan at alterapraxis.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

---

 src/util/mesa-sha1.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/util/mesa-sha1.c b/src/util/mesa-sha1.c
index faa1c87..ca6b89b 100644
--- a/src/util/mesa-sha1.c
+++ b/src/util/mesa-sha1.c
@@ -175,21 +175,24 @@ _mesa_sha1_final(struct mesa_sha1 *ctx, unsigned char result[20])
 #elif defined(HAVE_SHA1_IN_LIBGCRYPT)   /* Use libgcrypt for SHA1 */
 
 #include <gcrypt.h>
+#include "c11/threads.h"
+
+static void _mesa_libgcrypt_init(void)
+{
+   if (!gcry_check_version(NULL))
+      return NULL;
+   gcry_control(GCRYCTL_DISABLE_SECMEM, 0);
+   gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
+}
 
 struct mesa_sha1 *
 _mesa_sha1_init(void)
 {
-   static int init;
+   static once_flag flag = ONCE_FLAG_INIT;
    gcry_md_hd_t h;
    gcry_error_t err;
 
-   if (!init) {
-      if (!gcry_check_version(NULL))
-         return NULL;
-      gcry_control(GCRYCTL_DISABLE_SECMEM, 0);
-      gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
-      init = 1;
-   }
+   call_once(&flag, _mesa_libgcrypt_init);
 
    err = gcry_md_open(&h, GCRY_MD_SHA1, 0);
    if (err)